Lecture 6

We covered the relations chapter, looking at the definitions of reflexive, irreflexive, symmetric, antisymmetric, and transitive. Two major relation examples

• partial order: (charm, strength, health) triples, where x is better than y if all x's coordinates are better.
• equivalence relation: musical chords. For beginners, chords are considered "the same" if they have the same set of named notes.

We also proved transitivity and antisymmetry for the (charm, strength, health) triples,

Finally, we saw the big ideas for the functions chapters: onto, one-to-one, and not a function.